Coil spring biased printing wheels

ABSTRACT

The invention provides a printing device including a printing wheel which carries peripheral printing characters and peripheral ratchet teeth whereby it can be stopped at required printing positions. The wheel is of reduced width at and adjacent the ratchet teeth so that the printing characters can be of full width while a spring can be located at the part of reduced width and can extend out of the wheel to an external position of anchorage.

United States Patent 1191 1111 3,756,147 Gross et al. 1 Sept. 4, 1973 [54] COIL SPRING BIASED PRINTING WHEELS 2,818,801 1/1958 Hart et al [OI/99 O! 7 [75] Inventors: Henry Gross; Samuel Gross, both of $23,232? London, England 3,221,645 12 1065 Adler 101 95 3,269,510 8/1966 Peter 197/53 [73] Asslgnee g g g g fifif muted 3,307,676 3/1967 Hickerson 197/18 g 3,422,754 1/1969 Bakarojiev et al 10l/99 X [22] Filed: July 8, 1971 Primary ExaminerEdgar S. Burr [21] Appl' l60698 Assistant Examiner-Eugene H. Eickholt Attorney-Alexander & Dowell [30] Foreign Application Priority Data July 18, 1970 Great Britain 34,928/70 [57] ABSTRACT Aug. 21, Great Britain The invention provides a printing device including a printing wheel which carries peripheral printing char- 52 US. Cl. 101/95, 101/110 was and peripheral ratchet teeth whereby it can be [51 Int. Cl. B41 23/16 Stopped at required printing positions The wheel is f [58] held of Search 101/93 93 reduced width at and adjacent the ratchet teeth so that 101/96 7 the printing characters can be of full width while a spring can be located at the part of reduced width and [56] References Clted can extend out of the wheel to an external position of UNITED STATES PATENTS anchorage.

1,964,455 6/1934 Cook 101/28 2,363,253 11 1944 Larson u Clams 6 Drawmg F'gures 2,746,384 5/1956 Bradley et a1 101/93 R HF L,

[mil 1 l l l /8 l u fi PATENTEDSEP 4mm 3 756147 SHEEI 2 OF 3 PATENTEBSEP 4 ms 3356147 SHEET 3 (1F 3 VN va- COIL SPRING BIASEI) PRINTING WHEELS This invention relates to printing devices for use as part of a cash register, computer weighing machine or other machine involving a printing head especially of a kind in which the required data is transmitted to the devices in the form of electric impulses.

It is known to provide such devices with a continuously rotating printing cylinder but this involves a printing period of very short duration, e. g. one to two microseconds and this, in turn, involves critical control and great accuracy in construction with consequent high cost of production.

It is also known to provide printing wheels with driving mechanism which is stopped while printing is in progress. This gives good results with cheaper construction but nevertheless involves difficulty of accurately positioning the printing wheels during printing to take up backlash in the driving mechanism.

According to the present invention we provide a printing wheel having printing characters on one part of its periphery, ratchet teeth on another part of its periphery, a part of reduced thickness to receive a spring, and means for attachment of one end of the spring whereby the spring can be located within the overall width of the wheel. Thus the pawl-engaging teeth are integral with or fixed to the printing wheel so that there is no problem of backlash. A further important feature of the invention consists in providing the wheel with a concentric slot receiving a rod which serves to bring all the wheels back to their starting positions and which also is moved to allow the wheels to move until stopped by their pawls. The rod may be mounted on two arms pivotally arranged to rock about the same axis as the printing wheel.

The invention is illustrated by way of example in the accompanying drawings wherein:

FIG. 1 is an axial view from one direction of a printing wheel made in accordance with the invention;

FIG. 2 is a similar view but from the opposite direction;

FIG. 3 is a sectional view on the plane 3-3 on FIG. 2;

FIG. 4 is a sectional view on the plane 44 on FIG. 2;

FIG. 5 is an axial view of the wheel with some associated parts; and

FIG. 6 is a view of a number of wheels and associated parts seen at right angles to the axis.

The wheel 10 is a single integral member which may be formed by injection moulding of metal or a synthetic resinous material, e.g. polythene or a polyamide. The wheel has a segmental part from 11 to 12 which is thicker axially than the remainder segment 12 to 11. The thicker part 11 to 12 isprovided with peripheral printing characters 13 and the part 12 to 11 carries peripheral ratchet teeth 15. These teeth have their pawl engaging surfaces 17 undercut at a small angle to the adjacent radius 18 so as to hold a pawl 19 (FIG. 5) in the ratchet by the pressure of the surface 17 on the pawl under pressure of a spring 16.

The wheel has a central boss 20 which preferably has a marginally greater axial width as the part 11 to 12. The part 11 to 12 has grooves 21 on both sides and the boss 20 has grooves 22 on both sides, these grooves being only for the purpose of reducing the weight of the wheel. The grooves 21, 22 are omitted from FIG. 5 for the sake of clarity. The part 11 to 12 also has a slot 23 concentric with the axis of the wheel. The boss 20 has a groove 25 (FIG. 3) on its periphery at the part 12 to II, this groove serving to assist in holding the spring 16 in position.

The width of the part 11 to 12 which includes the teeth 15 is greater than the width of part 12 to 11 by an amount larger than the diameter of the spring so that the spring is located within the thickness of the printing wheel. This enables the spring 16 to extend out of the diameter of the printing wheel to an anchorage in the form of a pin 18 on a suitable part of the frame of the machine.

In the part 12 to 11 and adjacent one end of the slot 23, and the part 1 l is an opening 216 axially through the wheel. Extending over part of this opening is a flange 27 which carries a pin 28 which enters the opening 26 and serves to receive the end of the spring so that the spring will be partially guided by the surface 30 of the part 12 to 11 on to the pin.

A series of the printing wheels are mounted on a common spindle 32 so that adjacent wheels are in contact with each other as shown in FIG. 6. In other words, the wheels are not spaced apart by any mechanical devices.

A rod or bail 33 parallel to the spindle 32 passes through the slots 23 of all the printing wheels. This rod 33 is carried by arms (not shown) which are fixed to a pinion 37 driven by a toothed segment 38 from cam 39 so that the rod 33 can be driven in one direction to bring all the printing wheels to their rest positions and can be driven in the opposite direction to allow the printing wheels to rotate under the influence of the springs 16 until the printing wheels are arrested by the pawls 19. When all the printing wheels have been thus arrested a pressure member 40 is actuated to press a strip of paper and inking ribbon against all the printing characters along a generatrix of the assembly of printing wheels.

The pawls 19 are actuated by stems 44 which, in turn, are controlled by means including electro-magnetic devices 45.

The undercut surfaces 17 of the ratchet teeth hold the pawls in engagement even when the stems 44 desce'nd which occurs gravitationally or by springs when the current in the electro-magnetic devices ceases.

Each of the printing wheels has a part 46 of large enough radius to serve as a projection to carry the pawl out of the radius of the ratchet teeth when the wheels are moved back to starting positions. The pawls do however tend to drop out gravitationally at this time.

At least 250 of the periphery of the wheel may be occupied by the print and ratchet teeth each occupying approximately the same peripheral distance.

Instead of a helically wound wire spring it is possible to use a flat torsion spring in a recess in the wheel. The end of the spring may engage the shaft.

The wheel may have a greater or less number of printing positions depending on the size of the wheel and size of the printing characters. The wheel movement will generally not exceed We claim:

1. In a printing device having printing wheels rotated by coil springs, a printing wheel having a segmental part which is thicker axially than the remainder segmental part; printing characters on the periphery of one segmental part of the wheel;ratchet teeth on the periphery of the other segmental part of said wheel; the

segmental part of the wheel that carries the printing characters including a central boss having an axial thickness at least as great as the width of the printing characters axially of the wheel; the remainder segmental part of the wheel which includes the ratchet teeth and the part of the wheel between the ratchet teeth and the boss thereby being of reduced thickness to receive a coiled spring of smaller diameter than the difference in thicknesses between the said segmental parts, and means for attachment to one end of said spring, said means being located in the remainder segmental part of reduced thickness, whereby the spring can be located within the overall axial width of the wheel to extend partly around the boss and to extend beyond the periphery of the wheel for attachment to a fixed support.

2. A printing wheel as claimed in claim 1, said printing device including a pawl adapted to be moved into and out of engagement with pawl engaging faces on the said ratchet teeth; and the pawl engaging face of each tooth being undercut in the direction such that the outer end of this face will normally overlie the outer end of the pawl, whereby the face can hold the pawl engaged due to the pressure on said pawl by said face exerted by the said spring until said pawl is forced out.

3. A printing wheel as claimed in claim 2, said thicker segmental part having an arcuate slot thereon concentric with the axis of said wheel, a sprindle rotatably carrying said wheel; a rod passing through said arcuate slot and disposed parallel with said spindle; means in the printing device for supporting said rod whereby same can be driven in one direction to bring the printing wheel to a starting position, and can be driven in the opposite direction to allow the printing wheel to rotate under the influence of the spring until the wheel is arrested by said pawl; said rod serving to bring the wheel back to starting position by engagement with the end of said slot.

4. A printing wheel as claimed in claim 2, said remainder segmental part having at one end a peripheral portion of sufficient radius to serve to force the pawl out of engagement with the ratchet teeth.

5. A printing wheel as claimed in claim 1, said remainder segmental part having an opening therethrough at one end; and said attachment means comprising a projection on the wheel extending partly over the said opening, a pin on the projection located for attachment thereto of one end of said spring, said pin being located within the opening whereby the spring will be held onto the pin by engagement with the said remainder segmental part.

6. A printing wheel as claimed in claim 1, wherein the entire wheel is made in a single integral moulded piece.

7. A printing wheel as claimed in claim 1, having a groove in the boss to receive the said spring.

8. In a printing device as set forth in claim 3, said printing device having a series of wheels located side by side on a common spindle, together with said related coil springs acting thereon continuously urging the wheels in one rotary direction; the outer ends of the springs being anchored outside the diameter of the wheels, means to release all the wheels simultaneously whereupon they are rotated by the springs, and related pawls engageable with said teeth to stop the wheels in required positions.

9. A printing device as claimed in claim 8 wherein adjacent wheels are in contact with each other.

10. A printing device as claimed in claim 8, wherein each wheel has a peripheral part of large enough radius to serve to force its related pawl out of engagement with the ratchet teeth, and wherein the pawls are twoarmed, electromagnetic means for actuating the pawls, one arm of each pawl engaging the ratchet teeth and the other arm being actuated towards the ratchet teeth by said electromagnetic means, said pawls being held in the ratchet teeth by the pressure of the springs when the electromagnetic means is switched off until forced out of the ratchet teeth by said peripheral parts of large enough radius.

11. A printing device as claimed in claim 8, wherein each of the wheels has a concentric slot and a single rod engages in the slots of all the wheels, said rod being movable around the same axis as the wheels to restore the wheels to normal in one direction and to allow the wheels to move under the action of the springs in the other direction until stopped by the pawls.

i t k 

1. In a printing device having printing wheels rotated by coil springs, a printing wheel having a segmental part which is thicker axially than the remainder segmental part; printing characters on the periphery of one segmental part of the wheel; ratchet teeth on the periphery of the other segmental part of said wheel; the segmental part of the wheel that carries the printing chaRacters including a central boss having an axial thickness at least as great as the width of the printing characters axially of the wheel; the remainder segmental part of the wheel which includes the ratchet teeth and the part of the wheel between the ratchet teeth and the boss thereby being of reduced thickness to receive a coiled spring of smaller diameter than the difference in thicknesses between the said segmental parts, and means for attachment to one end of said spring, said means being located in the remainder segmental part of reduced thickness, whereby the spring can be located within the overall axial width of the wheel to extend partly around the boss and to extend beyond the periphery of the wheel for attachment to a fixed support.
 2. A printing wheel as claimed in claim 1, said printing device including a pawl adapted to be moved into and out of engagement with pawl engaging faces on the said ratchet teeth; and the pawl engaging face of each tooth being undercut in the direction such that the outer end of this face will normally overlie the outer end of the pawl, whereby the face can hold the pawl engaged due to the pressure on said pawl by said face exerted by the said spring until said pawl is forced out.
 3. A printing wheel as claimed in claim 2, said thicker segmental part having an arcuate slot thereon concentric with the axis of said wheel, a sprindle rotatably carrying said wheel; a rod passing through said arcuate slot and disposed parallel with said spindle; means in the printing device for supporting said rod whereby same can be driven in one direction to bring the printing wheel to a ''''starting'''' position, and can be driven in the opposite direction to allow the printing wheel to rotate under the influence of the spring until the wheel is arrested by said pawl; said rod serving to bring the wheel back to ''''starting'''' position by engagement with the end of said slot.
 4. A printing wheel as claimed in claim 2, said remainder segmental part having at one end a peripheral portion of sufficient radius to serve to force the pawl out of engagement with the ratchet teeth.
 5. A printing wheel as claimed in claim 1, said remainder segmental part having an opening therethrough at one end; and said attachment means comprising a projection on the wheel extending partly over the said opening, a pin on the projection located for attachment thereto of one end of said spring, said pin being located within the opening whereby the spring will be held onto the pin by engagement with the said remainder segmental part.
 6. A printing wheel as claimed in claim 1, wherein the entire wheel is made in a single integral moulded piece.
 7. A printing wheel as claimed in claim 1, having a groove in the boss to receive the said spring.
 8. In a printing device as set forth in claim 3, said printing device having a series of wheels located side by side on a common spindle, together with said related coil springs acting thereon continuously urging the wheels in one rotary direction; the outer ends of the springs being anchored outside the diameter of the wheels, means to release all the wheels simultaneously whereupon they are rotated by the springs, and related pawls engageable with said teeth to stop the wheels in required positions.
 9. A printing device as claimed in claim 8 wherein adjacent wheels are in contact with each other.
 10. A printing device as claimed in claim 8, wherein each wheel has a peripheral part of large enough radius to serve to force its related pawl out of engagement with the ratchet teeth, and wherein the pawls are two-armed, electromagnetic means for actuating the pawls, one arm of each pawl engaging the ratchet teeth and the other arm being actuated towards the ratchet teeth by said electromagnetic means, said pawls being held in the ratchet teeth by the pressure of the springs when the electromagnetic means is switched off until forced out of the ratchet teeth by said peripheral parts of large enough radius.
 11. A prInting device as claimed in claim 8, wherein each of the wheels has a concentric slot and a single rod engages in the slots of all the wheels, said rod being movable around the same axis as the wheels to restore the wheels to normal in one direction and to allow the wheels to move under the action of the springs in the other direction until stopped by the pawls. 